Python Tensorflow：必须为占位符tensor'；占位符'；使用dtype float[但该值是一个float]

我正在学习tensorflow教程，不断遇到以下错误：

InvalidArgumentError (see above for traceback): You must feed a value for placeholder tensor 'Placeholder' with dtype float
     [[Node: Placeholder = Placeholder[dtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]()]]

以下是回溯：

Traceback (most recent call last):
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/client/session.py", line 972, in _do_call
    return fn(*args)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/client/session.py", line 954, in _run_fn
    status, run_metadata)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/contextlib.py", line 66, in __exit__
    next(self.gen)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/framework/errors.py", line 463, in raise_exception_on_not_ok_status
    pywrap_tensorflow.TF_GetCode(status))
tensorflow.python.framework.errors.InvalidArgumentError: You must feed a value for placeholder tensor 'Placeholder' with dtype float
     [[Node: Placeholder = Placeholder[dtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]()]]

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "neural_network.py", line 48, in <module>
    print(sess.run(loss), feed_dict={xs:x_data, ys:y_data})
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/client/session.py", line 717, in run
    run_metadata_ptr)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/client/session.py", line 915, in _run
    feed_dict_string, options, run_metadata)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/client/session.py", line 965, in _do_run
    target_list, options, run_metadata)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/client/session.py", line 985, in _do_call
    raise type(e)(node_def, op, message)
tensorflow.python.framework.errors.InvalidArgumentError: You must feed a value for placeholder tensor 'Placeholder' with dtype float
     [[Node: Placeholder = Placeholder[dtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]()]]

Caused by op 'Placeholder', defined at:
  File "neural_network.py", line 21, in <module>
    xs = tf.placeholder(tf.float32,[None,1])
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/ops/array_ops.py", line 1332, in placeholder
    name=name)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/ops/gen_array_ops.py", line 1748, in _placeholder
    name=name)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/framework/op_def_library.py", line 749, in apply_op
    op_def=op_def)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/framework/ops.py", line 2380, in create_op
    original_op=self._default_original_op, op_def=op_def)
  File "/home/mddrill/anaconda2/envs/python35/lib/python3.5/site-packages/tensorflow/python/framework/ops.py", line 1298, in __init__
    self._traceback = _extract_stack()

正如您在这里看到的，x_数据和y_数据都是浮点数，所以我不明白为什么会出现这个错误

当我在sess.run（train_step，feed_dict={xs:x_data，ys:y_data}）之前添加一个print语句

print（type（x_data[0][0]），type（y_data[0][0]）

。我明白了：

很明显，它们都是浮点数

---

我错过了什么

您在

print（）

语句中有一个错误。幸运的是，在我使用TensorFlow r0.11时，它作为一个

SyntaxError

被我选中

取代

print(sess.run(loss), feed_dict={xs:x_data, ys:y_data})

有,

---

你使用TensorFlow r0.12吗？这确实节省了我几个小时。我有一个eval（）语句，但我忘了传递提要。谢谢！

print(sess.run(loss), feed_dict={xs:x_data, ys:y_data})

print(sess.run(loss, feed_dict={xs:x_data, ys:y_data}))